Polarized light is well-known, and is used in applications ranging from high speed data transfer to quantum communication. A polarizer (or polariser) is an optical filter that allows light waves of a specific polarization to pass and block light waves of orthogonal polarizations, and thus can convert a light beam of undefined or mixed polarization into a beam of well-defined polarization. Linear polarizers can be divided into two general categories being absorptive polarizers where the unwanted polarization states are absorbed by the optical device, and beam-splitting polarizers where a beam is split into two beams with orthogonal polarization states. Polarizers which maintain the same axes of polarization with varying angles of incidence are generally called Cartesian polarizers, since the polarization vectors can be described with simple Cartesian coordinates (e.g., horizontal vs. vertical) independent from the orientation of the polarizer surface. When the two orthogonal polarization states generated are relative to the direction of a surface (usually found with Fresnel reflection), they are usually termed s and p polarizations, where light polarized in the plane of incidence is said to be p-polarized, while light polarized perpendicular to the plane of incidence it is said to be s-polarized.
Typical optical polarization applications use light with a uniform polarization, meaning light beams or light modes that have the same polarization at any position across the transverse beam (transverse to the optical axis of the beam). However, more recently light beams with structured polarization, where the polarization state varies across the transverse beam profile, have gained interest for research involving non-classical light fields. In particular, for radially polarized light beams, so-called vector vortex beams, where at any position within the polarization (electric field) vector points towards the center of the beam, have become known for their unique properties, including their improved focusing properties, such as for microscopy and laser cutting, and in vector-vortex coronagraphs for state-of-the-art astronomical telescopes.
Some polarized light applications attempt to generate radial and azimuthal polarization states (where all polarization vectors are orthogonal to the radial case) and optical states with non-zero values of optical angular momentum. In practice, an array of waveplate segments may be used to provide an approximation to a radially polarized beam. More accurate methods for generating radial and azimuthal polarization states and optical states with non-zero values of optical angular momentum include the use of super-structured waveplates (S-waveplates) comprising laser nano-structured glass. Such S-waveplates can generally provide fine polarization state detail.